1. Field of the Invention
The present invention relates to a board assembly that includes a circuit board, an electronic component mounted on the circuit board, and another board bonded to the circuit board, to an ink-jet head that includes a circuit board, a driver IC mounted on the circuit board, and a piezoelectric actuator bonded to the circuit board, and also to a method for manufacturing them.
2. Description of Related Art
Some ink-jet heads include a passage unit in which many pressure chambers are formed, and a piezoelectric actuator that has active portions corresponding to the respective pressure chambers and is bonded to the passage unit. Surface electrodes corresponding to the respective active portions are provided on an upper face of the piezoelectric actuator. Terminals of a flexible printed circuit (FPC) for applying voltage to the piezoelectric actuator are bonded to the respective surface electrodes. The FPC is mounted with an IC chip (see Japanese Patent Unexamined Publication No. 2003-159795).
In order to mount an electronic component such as the IC chip on a circuit board, for example, terminals of the electronic component are gold-plated while wiring patterns on the circuit board are tin-plated, and then the gold-plated layers formed on the respective terminals of the electronic component and the tin-plated layers formed on the wiring patterns of the circuit board are brought into contact and subjected to a heat treatment, so that the gold-plated layers and the tin-plated layers are bonded by means of gold-tin eutectic bonding (see Japanese Patent Unexamined Publication No. 7-66362). Therefore, in order to manufacture the above-described ink-jet head, gold-plated terminals of the IC chip and tin-plated terminals of the FPC are brought into contact, and the gold-plated layers and the tin-plated layers are bonded by means of gold-tin eutectic bonding, so that the IC chip is mounted on the FPC.